Technological advancements along with the rapid development of the semiconductor integrated circuit (IC) industry reflect on the application and design of IC materials, leading to emerging products with miniature volume and complex structure. A smart power IC may include multiple power devices, such as high-voltage transistor and high-power transistor, and control circuits, such as low-voltage transistor and low-powered transistor, on a single wafer. Consequently, disposition of a guard ring on high-voltage-side regions and improving capacity and stability of the guard ring have become important issues for the design of IC wafers.
To ensure safety and no interference to devices other than the high-voltage-side region, the guard ring must be capable of isolating the high-voltage-side region from other devices effectively while possessing excellent voltage reduction capability and long-term stability. Therefore, the inventors have routinely tested semiconductor devices by using 1000 hours (hrs) of high temperature reverse bias reliability (HTRB) test. However, the inventors have found that existing guard rings were incapable of sustaining even 500 hours under 700V in the HTRB test. As a result, under limited size alteration, the present invention aims to provide a guard ring with high voltage sustainability and improved stability.